The cycling characteristics of silver were studied in a small watershed and lake in the Colorado alpine region. The sources of silver for the watershed were atmospheric fallout and washout, groundwater percolation, and cloud seeding. Monthly synoptic samples of snow, stream and lake water, groundwater, soil, sediment, sediment interstitial water, aquatic plants, benthos, seston, and fish were analyzed for two years. The biological samples were subjected to acid digestion while ammonium pyrrolidine dithiocarbamate-methyl isobutyl ketone (APDC-MIBK) extractions were performed on the aqueous samples. Silver in the sediment was extracted by iodide complexation.

1The silver concentrations showed marked seasonal variations in all ecosystem components studied, and this implied a partially reversible mechanism of bioaccumulation. Variations in silver concentration in the ecosystem components were statistically correlated on the basis of their physical and biological interactions, and these correlations provide a framework for an annual silver cycle. A chain of effects initiated by terrestrial climatological events is hypothesized to be causal in the levels of silver which eventually appear in aquatic biota and environments.